Modern semiconductor processing frequently involves photolithographic methods to pattern materials into very small structures, which are ultimately incorporated into a semiconductor circuit. An exemplary prior art method for forming small structures from a layer of material is as follows. First, the layer of material is provided over a semiconductive substrate. Subsequently, a layer of photoresist is provided over the layer of material. A photolithographic mask is then provided over the layer of photoresist and light is shined through the mask to expose portions of the layer of photoresist while leaving other portions unexposed. The photoresist typically comprises an unsaturated organic material, such as, for example, a material comprising one or more unsaturated carbon-containing rings. The exposed portions are rendered either more or less soluble in a solvent relative to the unexposed portions. If the exposed portions are rendered more soluble, the resist is referred to as a positive photoresist (as a positive image of a pattern from the photolithographic mask is transferred to the photoresist), and if the exposed portions are rendered less soluble, the photoresist is referred to as a negative photoresist (as a negative image of the pattern from the photolithographic mask is transferred to the photoresist). In any event, the photoresist is exposed to a solvent and either the exposed or unexposed portions are removed while leaving the other of the exposed or unexposed portions remaining over the layer of material. Such patterns the photoresist into a patterned mask overlaying the layer of material. The layer of material is then exposed to conditions which transfer a pattern from the patterned mask to the layer of material (i.e., which removes portions of the layer of material not covered by photoresist, while leaving the portions of the layer material that are covered by photoresist). Subsequently, the photoresist is removed and the substrate having the patterned layer of material thereon is subjected to subsequent processing steps to form an integrated circuit over the substrate.
Typically, the semiconductive substrate referred to above is in the form of a wafer and a plurality of semiconductor packages (i.e., individual integrated circuits) are simultaneously formed over the wafer. After the formation of the plurality of semiconductor packages is complete, the wafer is subjected to a die-cutting process to separate the individual integrated circuits from one another. In wafer fabrication processes employed to date, photoresist is entirely removed from a wafer prior to subjecting the wafer to a die-cutting process. Among the reasons for removal of the photoresist is that the photoresist is not a material suitable for incorporation into semiconductor circuits. It would be desirable to develop alternative methods for patterning structures during semiconductor circuit fabrication processes.
In an area of semiconductor processing considered to be unrelated to the above-described photolithographic processing methods, a recently developed technique for forming insulative materials is Flowfill™ Technology, which has been developed by Trikon Technology of Bristol, U.K. The process can be utilized for forming either silicon dioxide or methylsilicon oxide ((CH3)xSiO2−x), for example. The process for forming silicon dioxide is as follows. First, SiH4 and H2O2 are separately introduced into a chemical vapor deposition (CVD) chamber, such as a parallel plate reaction chamber. The reaction rate between SiH4 and H2O2 can be moderated by the introduction of nitrogen into the reaction chamber. A semiconductive wafer is provided within the chamber, and ideally maintained at a suitably low temperature, such, as 0° C., at an exemplary pressure of 1 Torr to achieve formation of a silanol-type structure of the formula Si(OH)x, which is predominantly Si(OH)4. The Si(OH)4 condenses onto the wafer surface. Although the reaction occurs in the gas phase, the deposited Si(OH)4 is in the form of a viscous liquid which flows to fill small gaps on the wafer surface. In applications where deposition thickness increases, surface tension drives the deposited layer flat, thus forming a planarized layer over the substrate.
The liquid Si(OH)4 is typically converted to a silicon dioxide structure by a two-step process. First, planarization of the liquid film is promoted by increasing the temperature to above 100° C., while maintaining the pressure of about 1 Torr, to result in solidification and formation of a polymer layer. Thereafter, the temperature is raised to above 400° C., while maintaining the pressure of greater than 1 Torr , to form SiO2. The processing above 400° C. also provides the advantage of driving undesired water from the resultant SiO2 layer.
The formation of methylsilicon oxide is accomplished similarly to that described above for forming silicon dioxide, with the exception that methylsilane ((CH3)zSiH4−z, wherein z is at least 1 and no greater than 4) is combined with the hydrogen peroxide to produce a methylsilanol, instead of combining the silane (SiH4) with the hydrogen peroxide to form silanol.